Why Are There 5,280 Feet in a Mile?


Why are there 5,280 feet in a mile, and why are nautical miles different from the statute miles we use on land? Why do we buy milk and gasoline by the gallon? Where does the abbreviation "lb" come from? Let's take a look at the origins of a few units of measure we use every day.

The Mile

The basic concept of the mile originated in Roman times. The Romans used a unit of distance called the mille passum, which literally translated into "a thousand paces." Since each pace was considered to be five Roman feet—which were a bit shorter than our modern feet—the mile ended up being 5,000 Roman feet, or roughly 4,850 of our modern feet.

If the mile originated with 5,000 Roman feet, how did we end up with a mile that is 5,280 feet? Blame the furlong. The furlong wasn't always just an arcane unit of measure that horseracing fans gabbed about; it once had significance as the length of the furrow a team of oxen could plow in a day. In 1592, Parliament set about determining the length of the mile and decided that each one should be made up of eight furlongs. Since a furlong was 660 feet, we ended up with a 5,280-foot mile.

The Nautical Mile

So if the statute mile is the result of Roman influences and plowing oxen, where did the nautical mile get its start? Strap on your high school geometry helmet for this one. Each nautical mile originally referred to one minute of arc along a meridian around the Earth. Think of a meridian around the Earth as being made up of 360 degrees, and each of those degrees consists of 60 minutes of arc. Each of these minutes of arc is then 1/21,600th of the distance around the earth. Thus, a nautical mile is 6,076 feet.

The Acre

Like the mile, the acre owes its existence to the concept of the furlong. Remember that a furlong was considered to be the length of a furrow a team of oxen could plow in one day without resting. An acre—which gets its name from an Old English word meaning "open field"—was originally the amount of land that a single farmer with a single ox could plow in one day. Over time, the old Saxon inhabitants of England established that this area was equivalent to a long, thin strip of land one furlong in length and one chain—an old unit of length equivalent to 66 feet—wide. That's how we ended up with an acre that's equivalent to 43,560 square feet.

The Foot

As the name implies, scholars think that the foot was actually based on the length of the human foot. The Romans had a unit of measure called a pes that was made up of twelve smaller units called unciae. The Roman pes was a smidge shorter than our foot—it came in at around 11.6 inches—and similar Old English units based on the length of people's feet were also a bit shorter than our 12-inch foot. The 12-inch foot didn't become a common unit of measurement until the reign of Henry I of England during the early 12th century, which has led some scholars to believe it was standardized to correspond to the 12-inch foot of the king.

The Gallon

The gallon we use for our liquids comes from the Roman word galeta, which meant "a pailful." There have been a number of very different gallon units over the years, but the gallon we use in the United States is probably based on what was once known as the "wine gallon" or Queen Anne's gallon, which was named for the reigning monarch when it was standardized in 1707. The wine gallon corresponded to a vessel that was designed to hold exactly eight troy pounds of wine.

The Pound

Like several other units, the pound has Roman roots. It's descended from a roman unit called the libra. That explains the "lb" abbreviation for the pound, and the word "pound" itself comes from the Latin pondo, for "weight." The avoirdupois pounds we use today have been around since the early 14th century, when English merchants invented the measurement in order to sell goods by weight rather than volume. They based their new unit of measure as being equivalent to 7000 grains, an existing unit, and then divided each 7000-grain avoirdupois pound into 16 ounces.


Early 18th-century steam engine entrepreneurs needed a way to express how powerful their machines were, and the industrious James Watt hit on a funny idea for comparing engines to horses. Watt studied horses and found that the average harnessed equine worker could lift 550 pounds at a clip of roughly one foot per second, which equated to 33,000 foot-pounds of work per minute.

Not all scholars believe that Watt arrived at his measurement so scientifically, though. One common story claims that Watt actually did his early tests with ponies, not horses. He found that ponies could do 22,000 foot-pounds of work per minute and figured that horses were half again stronger than ponies, so he got the ballpark figure of 33,000 foot-pounds of work per minute.

Will the Sun Ever Stop Shining?


Viktor T. Toth:

The Sun will not stop shining for a very, very long time.

The Sun, along with the solar system, is approximately 4.5 billion years old. That is about one-third the age of the entire universe. For the next several billion years, the Sun is going to get brighter. Perhaps paradoxically, this will eventually result in a loss of carbon dioxide in the Earth’s atmosphere, which is not good news; It will eventually lead to the death of plant life.

Within 2.5 to 3 billion years from now, the surface temperature of the Earth will exceed the boiling point of water everywhere. Within about about 4 to 5 billion years, the Earth will be in worse shape than Venus today, with most of the water gone, and the planet’s surface partially molten.

Eventually, the Sun will evolve into a red giant star, large enough to engulf the Earth. Its luminosity will be several thousand times its luminosity at present. Finally, with all its usable nuclear fuel exhausted and its outer layers ejected into space, the Sun’s core will settle down into the final stage of its evolution as a white dwarf. Such a star no longer produces energy through nuclear fusion, but it contains tremendous amounts of stored heat, in a very small volume (most of the mass of the Sun will be confined to a volume not much larger than the Earth). As such, it will cool very, very slowly.

It will take many more billions of years for the Sun to cool from an initial temperature of hundreds of thousands of degrees to its present-day temperature and below. But in the end, the remnant of the Sun will slowly fade from sight, becoming a brown dwarf: a cooling, dead remnant of a star.

This post originally appeared on Quora. Click here to view.

Why Do So Many Airports Have Chapels?

Inside Our Lady of the Airways Chapel at Boston Logan International Airport
Inside Our Lady of the Airways Chapel at Boston Logan International Airport

There are only so many ways to kill time during a long layover. You might browse the magazines at a Hudson News or take the time to test out a travel pillow or two. If it's a particularly trying travel day, you may want to while away a few hours at an airport bar. But if you’ve killed enough time in enough U.S. airports, you've probably noticed that most of them have chapels tucked into a corner of the terminal. Some of them are simple, some of them are ornate. Some cater specifically to members of one religion while others are interfaith. So where did they come from, and why are they there?

The biggest surprise in answering the latter part of that question might be that airport chapels weren't originally built for airport passengers at all. According to Smithsonian.com, the first U.S. airport chapel opened in 1951 at Boston's Logan International Airport and was specifically created for the airport’s Catholic staff, largely to offer mass services for workers on longer shifts.

Dubbed “Our Lady of the Airways,” Boston's airport chapel concept was quickly embraced by Catholic leaders around the country. In 1955, Our Lady of the Skies Chapel opened at New York City's Idlewild Airport (which was renamed John F. Kennedy International Airport in 1963). Other Catholic chapels followed.

In the 1960s, JFK added both a Protestant chapel and a Jewish synagogue to its terminals. By the 1980s, Protestant chapels had opened in the Atlanta and Dallas airports as well.

Single-faith chapels dissipated for the most part during the 1990s and into the new millennium. In 2008, The Christian Index ran a story about the changing face of on-the-go religious spaces and declared "Single-faith chapels a dying breed at U.S. airports." As interfaith chapels became the new normal, this inclusiveness extended to the chapels' patrons as well. Instead of remaining gathering places for airport employees, the chapels opened their doors to the millions of passengers traveling in and out of their cities each year.

Today, more than half of America's busiest airports feature chapels, the majority of which are interfaith. Most existing chapels are welcoming to people of all faiths and often include multiple religious symbols in the same room. They have become important spaces for meditation and reflection. Many of them still offer worship services for each of their represented practices, including places like the interfaith chapel at Washington Dulles International Airport, which hosts a Catholic mass on Saturday evenings as well as daily Jewish prayer services. Though each airport chapel is unique in design and services, they all endeavor to offer a much-needed spiritual refuge from the hassle of air travel.

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